Drainback vs. Closed Loop Circulators [RE-wrenches]

[Conrad Geyser]

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I think that this corrosion issue is what is at the heart of the drainback 
failure rate that we see.
If you make your drainback closed loop, i.e. non-vented, then maybe that's a 
way around this.  No oxygen introduction.
Otherwise, corrosion of the circulators and the collection loops definitely 
has been an issue.
One of our favorite ways to minimize summer overheating in our glycol 
systems is to put in a section of baseboard that is fed by a three way zone 
valve (Erie please).
Control the zone valve with an aquastaton the glycol loop set to 160 F. 
This works out well in the NE where most of the basements that we go in have 
dehumidifiers going all summer.  Another is a "vacation valve" that bypasses 
the check valve and allows reverse thermosiphoning at night(credit Bill 
Guiney).
Just hoping to avoid repeated mistakes...
Conrad G.
Cotuit Solar

----- Original Message ----- 
From: <solarpro at aol.com>
To: <RE-wrenches at topica.com>
Sent: Wednesday, June 07, 2006 9:56 PM
Subject: Re: Drainback vs. Closed Loop Circulators [RE-wrenches]


>
> Hello SHWrenches:
>
> Drainback systems for space heating is very good advice.  Even if you have 
> a
> "dump" load, pool/spa/geothermal, a closed or 'open' loop system will 
> overheat
> if (WHEN) something goes south.
>
> I've never come to closure on one issue re drainbacks - is it better to 
> use
> distilled/de-ionized water or tap water?  I understand that "tap" water 
> covers
> a lot of territory, but the only drain-backs I have had serious problems 
> with
> were systems using distilled water - actual copper tubing failure 
> unrelated to
> erosion corrosion.  I've seen waterways turn to copper foil.  I suppose it
> could have been due to high heat in a moist environment but somebody a 
> long time
> ago told me that distilled water is "hungry" and will eat away metals.  It
> does seem that the best way to resolve this issue is to use a buffered 
> glycol,
> but pump head and heat absorption do suffer.
>
> Anybody copy my experience with distilled or de-ionized water?
>
> Patrick A. Redgate
> AMECO
> Long Beach, CA
> (562) 595-9570
> www.amecosolar.com
>
>
> In a message dated 6/7/2006 5:14:18 PM Pacific Standard Time,
> conradg at cape.com writes:
>
> Hi Ken,
> No confusion between Draindown and Drainback here.
> And I don't mean to imply that our experience with drainbacks is 
> universal.
> Just reporting in from the feild without a lot of detail.
> My opinion on the issue is that you go to a drainback for a space heating
> system but stick to a closed loop for SDHW.
> your glycolhead,
> Conrad Geyser
> Cotuit Solar
>
>
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